A variety of conditions are characterized by an organism's inability to maintain the hemodynamic stability of its circulatory system. In many conditions, hemodynamic instability is associated with an organism's failure to perform one or more of the following normal functions: detoxify blood, metabolize products in the blood, synthesize products required for the maintenance of hemodynamic stability, and modulate factors from the hormone or immune systems. Prominent examples of conditions that result in hemodynamic instability include loss of organ function and sepsis.
Loss of organ function is a serious risk to survival of an organism. A number of approaches to compensate for the loss of organ function have been developed. The ability to compensate for loss of an organ's function varies with both the organ that fails and the type of organ failure. For example, loss of kidney function can be treated with extracorporeal blood treatments that involve passing a patient's blood through a hemodialysis device. The hemodialysis device purifies a patient's blood using a dialysate that promotes diffusion of toxins from the blood to the dialysate. In many cases hemodialysis treatment can continue for years after the patient has lost substantial kidney function.
Liver failure, on the other hand, has proven more difficult to treat. The mortality rate for acute hepatic failure remains alarmingly high (over 50%). No effective therapy has been developed for the treatment of acute liver failure, and survival is best ensured only after total liver replacement by transplantation. Although liver transplants have a good success rate for curing patients with liver failure, ˜90%, transplantation is not a viable option for the majority of persons suffering from liver failure for several reasons. First, the high cost of liver transplants effectively places transplantation beyond the reach of many patients. Second, many patients forgo transplant procedures because of the widely recognized shortage of donor livers available for transplantation. In 2002, 5,329 liver transplant procedures were performed, despite the fact that over 17,000 people were on the United States' national waiting list for a donor liver. (Source: Organ Transplantation Network (OPTN) web site, Richmond, Va.). From Jan. 1, 1995 to Oct. 31, 2004, 15,281 persons died while on the waiting list for a donor liver, and an additional 4,009 patients were removed from the waiting list because they were “too sick” for a transplant operation.